Glycerol fermentation process



Patented Aug. 7, 1945 I I v f UNITED-'- STATES. 'PATENT OFFICE a onrcanonlm (inns rnoons's I Howard M. Hodge, nllflllcllm Hflllil, M1, 18-

signor, by mesne assignments, to U. S. Industrial Chemicals, Inc., a-oorporation of Delaware No Drawing. Application February 1:, 1m,

sci-n No. 318,705

, 6 Claims. lei. 195-48). 4 It is well established that. sulfltes, bisulfltes, states on'page 130, llne6: Normally-i. e., at pH alkaline carbonates, .molasses ash' and other 111- 6.8 to say pH 3.5, 91% to 94% of the sugar ferkaline materials, whenadded to a yeast fermentmented undergoes the usual Gay-Lussac reaction; ing sugar solution so as to produce an alkaline while glycerol is formed to an amount representmash, increase the yield of glyc'erolabove that ing 3% to 4.5% ofthe sugari' obtained in the normal alcoholic fermentation. .It has now been found that glycerol is formed 4 It is also generally conceded that it is desirable in greatly increased amounts by yeast in fermentto employ relatively cheap sources of sugar, such ing solutions if the pH is maintained between pH as molasses, if fermentation glycerol is to compete .6.0 and pH 7.0, and preferably 'betweenpH 6.4' with glycerol obtained by other ocesses. l0 and pH; 7.0. in the resence of ammonium com- Adisadvantage inherentinth majority of prepounds in an amount considerably above that viously described glycerol fermentation processes required for nutrition of the yeast. It becomes is the large amount of salts or alkalies required unnecessary to maintain the pH on the alkaline to obtain a commercially valuable glycerol yield; side and furthermore a small concentration of If, for example, a mash containing 100 tons of ammonium ions suflices for the function of this sugar were fermented by. the soda ash process of a ency in the desired increase in glycerol.

Eoil', or the sulflte process of Connstein and As sources of ammonium ions or ammonium Liidecke, over 30 tons of salts would have'to be compounds in the mash, ammonia gas, aqua amadded to the fermenter. If the molasses-ash monia, and in general the ammonium salts that process as described by Lawrie were used. over 50 are non-toxic to yeast (ammonium chlorid, am-

tons of molasses ash would be required. The 'usemonium sulfate, ammonium phosphate, ammoniof such large quantities adds so materially to the um carbonate, for example) are suitable, and one costs and difllculties of these processes as to render or more of these agents ma be employed. The them impractical' quantity of such material should be limited; In general, previously described glycerol ferotherwise there is likelihood of diminished glycmentation processes have called for an alkaline erol formation or even of failure of the fermen-' reacting mash. The use of an alkaline mash tatlon. On the other hand, the amountof am- 1 greatly increases the infection hazard-an item monia or its equivalent added to the mash is in of considerable importance in plant operation. excess of that which'would be adequate 'solely for. If the usual practice is foll wed and highly al- 'yeast-nutrition in a commercial fermentation. kaline materials are added/ at intervals to the To, keep' the fermenting mash solution within the mash, yeast activity is stopped upon each addistated DH range any nonenitrogenous neutralizer, tion. Usually it takes from twp to three hours n-toxic to yeast, for example, lime, mayheused. after each addition for the yeast to recover. Dur- %e additions of ammonia, gaseous or aqueous, ing these" periods. there i an excellent vopporor ammonium salts, one or more, are tobe within tunity for contaminating organisms .to develop. such amounts that the ammonia equivalent i be- Furthermore, this shar interference with thetween,0.1% and 1.0%, and P f y etween normal'yeast activity makes the fermentation pre- 0.2%" and 0.5%, by weight of the mash. 1 If 30%.

carious and thus requires close control. It would, aqua ammonia is used the optimum amount theretherefore, be} distinct advantage to utilize an 40 of'is approximately 10% by volume of the mash. acid medium for glycerol production and espethe equivalent being Since the cially advantageous if a continuous, uninteramounts of ammonia or its equivalent-and lime -i1ipted fermentation were to ensue. or itsequivalent are small. the disadvantage of Glycerol production above about 3%-4% 0': the loading the fermentation with large amounts of sugar fermented in an acid medium, except fora salts is overcome.

proposal involving a large quantity of neutral In carrying out this fermentation itis advansalts, has never been anticipated. Connsteln and taseous. though not absolutely essential. o emkg i U, 5, P t t. N 1,511,754, page 1, ploy the two-stage glycerol operation described by lines 52-57, state: one causes, as hitherto 1'3. M. Hildebrandt and N. M. Erb in-U. S. Patent usual,. sugaror-starch to ferment in neutral or No. 2,169,245, dated August 15, 1939.

acid solution only small amounts of propantriol In general outline, the preferred mode of carare formed, whereas acids are'formed which inrylngout theinstant invention is as follows: lure the isolation of the small amounts of pro- A yeast crop is'grown by aeration in a dilut pantrlol obtained." In a similar vein, Lawrie sugar mash, preferably a still-residue fro'm a in hismonograph, "Glycerol and the glycols," previous ethanol or glycerol fermentation. After tity molasses is added to raise the sugar content of the mash to -20 grams per 100 cc.- Fermentation sets in promptly, and then suiflcient aqua ammonia is added to bring the pH of the mash to 6.5-6.8. As the fermentation continues, hy-

drated lime is added when necessary to maintain the pH of the mash between 6.0 and 1.0.

Although the ammonium salts may be used, it is preferable to use aqua ammonia. The aqua ammonia or its equivalent mentation supplies ammonium ions or ammonium compounds for increased glycerol production. The small amount used has a stimulating action in the fermentation, and thus enables one to employ a higher sugar concentration than would otherwise be permissible. Since the fermentedout mash is already acid, it is necessary, before v distilling oil the ethanol, only to acidity it slightly to pH 6.0 if it has not reached this point. At pH 6.0 the ammonia is non-volatile during the distillation and does not contaminate the alcohol distillate. Any neutralizer other than lime that is nontoxic to yeast may be employed to keep the fermenting mash at the desired pH, examples being dolomitic lime, soda ash, alkaline oxides and hydroxides such as those of sodiumand potassium, and alkaline carbonates such as the carbonates of potassium and sodium. Lime is preferred because of its-strength as a neutralizer, its cheapness and availability. When lime is used its solubility is increased by the ammonia or ammonium salts.

.The following examples illustrate the invention vious ethanol fermentation were put into a clean fermenter, cooled to 90-F.,' and 2' lbs. of ammonium sulfate were added as a yeast nutrient. The mash was then inoculated with 2 ghllons of active yeast cultureand aerated for 17 hours. Microscopic examination at this time showed that a good yeast crop had developed. 166 gallons'of molasses were'then added overa period of two 'hours to give a sug'arconcentration of 20.25

grams per 100 cc. Aeration wasthen discon= tinued'and fermentation started immediately; 5 gallons of aqua ammonia were then added, which changed the mash from After 26 /2 hours 5 lbs..oi freshly slaked'. lime in three gallons of water were added, raising'the pH from 6.49 to 6.10. At 30 hours'a second quanof 5 lbs. of lime was added, changing the pH from 6.46 to 6.66. of 5 lbs. of lime was added which brought the pH from 6.50 to 6.70. The fermentation was then allowed to go to completion with no further additions, fermentation being complete at 70 hours at pH 6.07. Analysis showed 2.66 grams of glycerol and 6.99 grams of ethanol per 100 cc. The lime used amounted to 1.25% of the sugar contained inthe molasses used.

#2) A yeast crop was grown in 525 gallons of still residue by aeration as described in Example #1. After 18 hours aeration 179 gallons of molasses were'added over a period of 2 /2 hours to give a sugar concentration of 20.51 grams per 100 cc. Aeration was discontinued and 7 gallons of 30% aqua ammonia were then added, raising the pH from 5.6 to 6.66." At 22, 24, 29 and hours separate doses each of 5 lbs. of freshly slaked lime in 3 gallons'of water were added to maintain the pH of the mash between 6.60 and- 6.90. Fermentation was then allowed to go to pH 5.80 to 6.80.

At 31% hours a third dose as used in this ier- 1) 550 gallons of still-residue-from a prea good yeast crop has developed (12-24 hours), completion with no further additions and was complete at 69 hours at pH 6.48. Analysis of the beer showed 3.38- grams of glycerol and 7.03 grams of ethanol per 100 cc. The lime used amounted to 1.66% on the sugar basis.

It is not necessary to perform this fermentation in two stages, as the following example will show. However, if the two-stage process is not used, the mash should be pastuerized in order to get-the best results. This adds to the cost of operation.

(#3) A mash consisting of 350 gallons of still residue from a previous ethanol fermentation, 175 gallons of molasses, and 202 gallons of water, was pastuerized, cooled and seeded with 2 gallons of active yeast culture. This mash contained 20.00 grams of sugar per 100 cc. After and 7 gallons of aqua ammonia were added, changing the pH from 5.70 to 6.75. At 26 and 3'1 hours 5 lbs. of freshly slaked lime in 3 gallons of water were added, maintaining the pH of the mash between 6.51 and 6.90. The mash was then allowed to ferment out with no further additions and was'complete-at89 hours at pH 6.44;- The, beer contained 3.42 grams of glycerol and 5.96 grams of ethanol per 100 cc. The lime used amounted to' .84% of the total sugar.

To illustrate the use of an ammonium salt in place of ammonia and a non-nitrogenous neutralizer other than lime, the following is given:

(#4) 800 cc. quantity of still residue from a previous ethanol fermentation of molasses was inoculated with 5 cc. of an active yeast culture and aerated for 16 hours. At this time a large number of active yeast cells had developed, and 300 grams of blackstrap molasses was added, giving a sugar concentration of 17 grams per 100cc. To this mash of 1 liter volume there were added 5 grams of technical ammonium chlorid, as a source of ammonium ions. Fermentation set in promptly and 10 grams of soda ash were added, changing the pH of the mesh from 5.8 to 6.8., At 28 hours 5 grams of soda ash erol and 5.38 grams of ethanol per 100 cc. of beer.

The soda ash used amounted to 10.6% of the total sugar.

While it is preferable to employ non-nitrogenous neutralizers in maintaining the critical pH range. this is not glyc'erine yields can be obtained, under the invention by using a non-toxic alkaline ammonium compound, in sufllcient quantities, both as a source of ammonium ions and as a neutralizer to substantially keep the pH within the values stated.

This may be accomplished, for example, bythe addition, or additions, of ammonium carbonate in total amount approximating 10% on the sugar basis, withoutthe addition, also, of a non nittog- 18 hours, fermentation was vigorous absolutely essential, since fair in a second glycerol fermenunique and desirable advantages.

. to that formed in the second fermentation. In

this manner the glycerol content of the beer can be gradually increased to a higher level by slopping back of glycerol-containing still residue. For example, 1500 cc. amount of still residue from a glycerol fermentation made by the process here described and containing 3.04 grams of glycerol per 100 cc. was diluted with water to 3000 cc., inoculated with 10 cc. of active yeast culture and aerated for 16 hours. Microscopic examination at this time showed the presence of a large number of yeast cells. Sufficient blackstrap molasses was then added to give a sugar concentration of 19 grams per 100 cc. Fermentation set in promptly and 1% of the mash volume (38 cc.) of aqua am-' Whether the process is worked as a one-stage or i a two-stage operation, the control of the DH of the mash is essential. Experience indicates that the optimum range is pH 6.4-pH 7.0.

From'the foregoing it will be evident that this new process for glycerol fermentation has certain Thus, the fermentation is carried out in an acid mash, whereby the infection hazard is greatly reduced. The glycerol promoting agents-ammonia or ammonium salts and lime or the like-are required in low concentrations. Because of the small amounts of neutralizers required, the yeast cells are not subjected to drastic changes in pH, fermentation is not arrested upon each addition and a continuous uninterrupted fermentation ensues. The glycerol content of the beer can be increased to a higher level by slop'ping back of the non-toxic glycerolbearingstill residue.

' I claim:

1. Process for carrying out uninterrupted yeast -fermentation of sugar solutions, which is characterized by addition of material of the group consisting of ammonia and ammonium salts nontoxic to yeast in amount sufllciently in excess of the nutrient requirements of the yeast to promte the formation of glycerol, and maintenance of the pH of the fermentation solution between pH 6 and pH 7 by addition of one or more non-toxic neutralizers.

2. Process for carrying out uninterrupted yeast fermentation of sugar solutions, which is characterized by addition of material of the group consisting of ammonia and ammonium salts nontoxic to yeast in amount sufficiently in excess of the nutrient requirements of the yeast to promote the formation of glycerol, the amount added of such material being equivalent to 0.1%-1.0% NH3, and maintenance of the pH of the fermentation solution between pH 6 and pH 7 by addition of one or more non-nitrogenous non-toxic neutralizers.

3. Process for carrying out uninterrupted yeast fermentation of sugar solutions, which is characterized by addition of material of the group consisting of ammonia and ammonium salts nontoxic to yeast in amount sufllciently in excess of the nutrient requirements of the yeast to promote the formation of glycerol, and maintenance of the pH of the fermentation solution between pH 6 and pH 7 by addition of lime.

4. Process for carrying out uninterrupted yeast fermentation of sugar solutions, which is characterized by addition of aqua ammonia in such amount that the NH": equivalent thereof is between 0.1% and 1.0% by weight of the mash, to promote the formation of glycerol, and maintenance of the pH of the fermentation solution between pH 6 and pH 7 by addition of lime.

5. A glycerol fermentation process, which comprises growing a yeast crop in a low sugar mash with aeration, greatly increasing the sugar concentration of the mash and discontinuing aeration, adding material of the group consisting of ammonia and ammonium salts non-toxic to yeast in amount. sufliciently in excess of the nutrient requirements of the yeast to promote the formation of glycerol, and maintaining the pH of the fermentation solution between pH 6 and pH '1 by addition of one or more non-toxic neutralizers.

6. The process as characterized in claim 5 in which the low-sugar yeast growing mash comprises still residue from a previous yeast fermentation.

HOWARD M. HODGE. 

